The invention concerns a knee-joint endoprosthesis whose femoral part displays, at the lower end, two condylar pans, and whose tibial part displays a tibial plateau, with each condylar pan displaying a downwardly-running lateral wall, and a supporting wall running outwardly from the lateral wall for resting against the tibial plateau. These types of knee-joint endoprostheses are, for example, known as axle-free endoprostheses or, from DE 40 02 424 A1, in the form of so-called axle-knee endoprostheses. Shaping and dimensioning of the known-type, knee-joint endoprostheses allows for achieving an exact-as-possible imitation of the statics and mechanics of the natural knee joint--with a simple construction of the prosthesis. However, it has been shown that, short term or long term, after implantation of a known-type, knee-joint endoprosthesis, pain then frequently appears when the knee cap and corresponding ligamentous apparatus are preserved at the time of implantation.
It is further known to join the support areas of the two condylar pans ventrally and to lengthen them upwardly such that the ventral tip of the support areas covers the natural condyles in a region in which, with a bending movement, the patella (knee cap) comes to rest under pressure against the condyles. In the case of this known endoprosthesis, the knee cap lies against the smooth surface of the drawn-up support areas and not against the natural condyles. However, it has been shown that even the realization of a patella counter support of this type can not always prevent the difficulties appearing in the region of the knee cap with longer-term usage of the prosthesis.